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首页> 外文期刊>Applied Geochemistry: Journal of the International Association of Geochemistry and Cosmochemistry >Microbial, redox and organic characteristics of compacted clay-based buffer after 6.5 years of burial at AECL's Underground Research Laboratory
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Microbial, redox and organic characteristics of compacted clay-based buffer after 6.5 years of burial at AECL's Underground Research Laboratory

机译：在AECL地下研究实验室埋藏6.5年后，压实粘土基缓冲液的微生物，氧化还原和有机特性

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摘要

Many countries are considering options for long-term management of nuclear waste. One common aspect among deep geological disposal options in granitic host rock is the use of clay-based buffer materials to limit radionuclide migration in case of container failure. The isothermal test (ITT) involved placing similar to2.4 m(3) of clay-based buffer in a bore-hole at the 240 m level of AECL's, Underground Research Laboratory to study the response of buffer to resaturation by groundwater over a 6.5-year period. Results are reported here on measurements taken at the end of the test for microbial, redox and organic characterization of the buffer. Results from enumerations and biomass determinations suggested that the viable population of cells in the buffer was several orders of magnitude larger than could be cultured. It is postulated that, due to the constrictive and nutrient-poor buffer environment, viable and active cells became stressed during burial and lost activity and culturability but not viability. Culturable microbial populations at interfaces in the ITT were about an order of magnitude larger than in comparable bulk buffer samples, suggesting that interfaces may be preferred sites for microbial activity and transport. The presence of culturable SO4-reducing bacteria and an increase in solid sulphide concentrations in the buffer suggested SO4 reduction, which appeared to be very variable locally. Only about 0.02-0.5% of SO4 was converted to sulphide, suggesting that SO4 reduction was not (yet) a dominant process. No methanogens could be enumerated from the ITT, and phospholipid fatty acid (PLFA) profiles did not suggest their presence. Gas analysis of samples recovered from the ITT suggested some reduction in O-2 near the top of the experiment, but deeper samples did not show a significant decrease in O-2 and had only a small increase in CH4 and H, levels. This suggested that microbial processes were depressed in the buffer but may have been more active near the concrete/buffer interface. The suggestion. of low microbial activity in the buffer was corroborated by the results from the PLFA analysis, which indicated low biomass turnover rates-and starvation biomarkers. The combination of enumerations, PLFA and gas analysis results suggested that no significant evolution-towards reducing conditions occurred during the duration of the ITT. Fulvic acids made up the largest, fraction of water-leachable humic substances but accounted for only about 2% of the total C inventory of the buffer material. The complexing capacity of these humic substances, based on carboxylic functional groups, ranged from 24 to 32 meq/g dissolved organic C. This may provide buffer porewater with considerable complexing capacity for radionuclides. Crown Copyright (C) 2002 Published by Elsevier Science Ltd. All rights reserved. [References: 46]
机译：许多国家正在考虑对核废料进行长期管理的备选方案。花岗岩基质岩石中深层地质处置方案中的一个常见方面是，在集装箱发生故障的情况下，使用粘土基缓冲材料来限制放射性核素的迁移。等温测试（ITT）涉及将约2.4 m（3）的粘土基缓冲液放置在AECL 240 m水平的钻孔中，地下研究实验室研究6.5对缓冲液对地下水再饱和的响应年期间。在此报告了测试结束时对缓冲液的微生物，氧化还原和有机特性进行测量的结果。枚举和生物量测定的结果表明，缓冲液中的活细胞种群比培养的细胞大几个数量级。据推测，由于狭窄和营养缺乏的缓冲环境，在埋葬期间存活和活跃的细胞变得紧张，失去活性和可培养性，但没有存活力。 ITT中界面处的可培养微生物种群比可比的大量缓冲液样品中的可培养微生物种群大约大一个数量级，这表明界面可能是微生物活动和运输的首选场所。可培养的可减少SO4的细菌的存在以及缓冲液中固体硫化物浓度的增加表明SO4的减少，这似乎在本地变化很大。只有约0.02-0.5％的SO4转化为硫化物，表明SO4还原还不是主要过程。从ITT中无法列举出产甲烷菌，并且磷脂脂肪酸（PLFA）谱图并不表明它们的存在。对从ITT回收的样品进行的气体分析表明，在实验顶部附近O-2有所减少，但较深的样品并未显示O-2显着下降，而CH4和H的含量仅小幅增加。这表明缓冲液中的微生物过程受到抑制，但在混凝土/缓冲液界面附近可能更活跃。该建议。 PLFA分析的结果证实了缓冲液中微生物活性较低的原因，这表明生物质周转率和饥饿生物标志物较低。枚举，PLFA和气体分析结果的组合表明，在ITT期间，没有发生明显的向减少方向发展的情况。黄腐酸是最大的水可溶腐殖质部分，但仅占缓冲材料总碳储量的2％。这些腐殖质基于羧基官能团的络合能力范围为24到32 meq / g溶解的有机碳。这可以为缓冲孔水提供对放射性核素相当大的络合能力。 Crown版权（C）2002，由Elsevier Science Ltd发布。保留所有权利。 [参考：46]

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